In a signaling system 7 (SS7) network, signal transfer point (STP) nodes are employed to route SS7 signaling messages through the network. Conventional STP routing, as defined in Bellcore/Telecordia standard GR-82-CORE, Issue 5, December 2001, involves SS7 message routing based on a destination point code (DPC) value contained in a message transfer part (MTP) routing label in an SS7 message. Such routing is commonly referred to as MTP routing. A sample SS7 message signaling unit (MSU) 100 is shown in FIG. 1. In FIG. 1, MSU 100 includes an originating point code (OPC) 102 and a DPC 104. In the case of signaling connection control part (SCCP) messages that require global title routing, a global title routing address translation step is required before MTP routing is performed. However, in either case, the DPC contained in the MTP routing label of an SS7 message is used to determine over which SS7 signaling linkset the message should be transmitted.
Signaling links connected to an STP are organized into groups of up to 16. Each group is known as a linkset. Furthermore, all signaling links in a given linkset must terminate at the same adjacent node. In the case of a combined linkset, all signaling links in a given linkset must terminate at the same mated pair of adjacent nodes. STP nodes are typically provisioned to distribute message transmission across all of the links in a linkset for load sharing purposes.
In addition to signaling links and linksets, a routing entity, commonly referred to as a signaling route, is also defined at an STP. A signaling route may include one or more signaling linksets. An STP may maintain a cost value associated with each route, and route availability is affected by received network management information. When multiple routes exist to the same destination, the STP may select the lowest cost route to the destination. Thus, all messages received at an STP that are addressed to a particular DPC will be routed to the destination via the first available, lowest cost route, where overall route selection is based on the DPC specified in the message being routed. Such a routing mechanism ensures that a message will be routed to the appropriate DPC, but there is no way using conventional routing procedures to control the exact path or route taken by the message based upon who is sending the message.
To illustrate conventional MTP routing, a sample SS7 network 200 is presented in FIG. 2. In FIG. 2, signaling network 200 includes a pair of originating end office (EO) nodes 202 and 204, a first STP node 206, a second STP node 208, a third STP node 210, and destination end office 212. Originating end office 202 has an SS7 point code of 244-2-1 and is coupled to STP 206, which has a point code of 1-1-1. Signaling linkset LS3 interconnects end office 202 and STP 206. As such, the point code 244-2-1 is referred to as an adjacent point code (APC) with respect to STP 206. Similarly, originating end office 204 has a point code of 5-2-1 and is coupled to STP 206 via signaling linkset LS4. STP 206 is coupled to adjacent STP 208 via LS1. STP 208 has a point code of 10-10-10. STP 206 is coupled to adjacent STP 210 via LS2. STP 210 has a point code of 248-10-10.
Table 1 shown below illustrates exemplary routing data that may be maintained by STP 206. In Table 1, the exemplary routing table includes a Route DPC field, a LinkSet field, a LinkSet APC field, and a Route Cost field. The information contained in Table 1 is used by routing logic in STP 206 to determine how to direct or route a received message. In the message routing scenario illustrated in FIG. 2, STP 206 receives a first SS7 signaling message M1 from originating EO 202. For purposes of illustration, it is assumed that message M1 is addressed to the DPC 145-2-1, which corresponds to EO 212. Upon receiving message M1, routing logic in STP 206 accesses the routing information contained in Table 1 and selects an outbound signaling linkset associated with the lowest cost route to 145-2-1. In this example, the selected signaling linkset is LS1, which is connected to adjacent STP 208. Consequently, the message is transmitted to STP 208 via linkset LS1. STP 208, upon receiving the message M1, performs similar routing processing and transmits the message across another signaling linkset to destination EO 212.
TABLE 1Routing InformationRoute DPCLinkSetLinkSet APCRoute Cost145-2-1LS1 10-10-1010LS2248-10-1020 10-10-10LS1 10-10-1010248-10-10LS2248-10-1010244-2-1LS3244-2-110 5-2-1LS4 5-2-110
In the second message routing scenario illustrated in FIG. 2, a message M2 is sent by end office 204. The DPC in the message is set to 145-2-1, which corresponds to EO 212. Message M2 is received by STP 206, which again accesses the routing information contained in Table 1 and selects an outbound signaling linkset corresponding to the lowest cost route to 145-2-1. Once again, the lowest cost route is selected, which corresponds to signaling linkset LS1 (assuming LS1 is not congested or out of service) and the message M2 is transmitted to STP 208 via linkset LS1. STP 208, upon receiving message M2, transmits the message to destination EO 212.
The routing process illustrated above has significant drawbacks in situations where network operators need the ability to control the routing of some or all signaling messages traversing a network. For example, as shown in FIG. 3, a network operator may install a high-speed, highly reliable signaling linkset LS5 that directly connects STP 206 and EO 212. The network operator may desire to charge a premium for signaling traffic that uses LS5 and may enter an agreement with the owner of EO 204 to ensure that all signaling messages originating from EO 204 are routed via the high-speed, reliable linkset LS5. Given the routing mechanisms currently utilized in SS7 signaling networks, there is no means for STP 206 to guarantee that messages from EO 204 will be routed via LS5.
U.S. Pat. No. 5,384,840 discloses a system for routing signaling messages to different destinations using network endpoint STPs (NESTPs) based on the nodes that are immediately adjacent to the NESTPs. However, in large telecommunications networks, the end office that originates a signaling message may not be adjacent to the node that routes the signaling message to the destination. FIG. 4 illustrates this problem. In FIG. 4, an STP 214 is located between end offices 202 and 204 and STP 206. As a result, if STP 206 implements a routing scheme such as that described in the '840 patent that relies on the immediately adjacent node to select an outbound signaling linkset, both signaling messages M1 and M2 will be routed over the same linkset, even though they originated from different end offices. Such a routing scheme is unsuitable for networks in which service providers wish to provision high-speed or high-reliability routes and selectively route messages over the high-speed or high-reliability routes independently of intermediate networks.
Therefore, there exists a long felt need for methods and systems for selecting a route among multiple routes to the same destination so that signaling messages from a particular source can be guaranteed to be transmitted over a particular routing schema independently of the intermediate network.